394 Journal of Agricultural Research voi. xix.No.g 



be a connecting link between the various studies. In this paper the 

 results with the Hannchen variety are given in full for one year at 

 Aberdeen, Idaho. The Hannchen variety was chosen for this basic 

 statement because it has been used more extensively than any other 

 variety. The growth at Aberdeen is selected both because of the fact 

 that most of the studies made and projected are located there and 

 because of the remarkable uniformity of growth of plants at that place 

 from season to season. In three different years the period from flowering 

 to maturity has extended over exactly 26 days. This uniformity, 

 coupled with accurate sampling, has made it possible to take samples 

 at intervals as short as 24 hours or even less and still show consistent 

 growth. In no previous studies on cereal crops, either here or abroad, 

 have samples been taken more frequently than at 3-day intervals, yet 

 it is readily seen in figure i that most of the growth in length is com- 

 pleted in a period of three days. The measurements of kernel dimen- 

 sions are an important index of development which seems to have 

 been generally ignored. 



HISTORICAL REVIEW 



The published data on kernel development have little relation to the 

 various lines of investigation at Aberdeen, Idaho. Dififerences of location 

 and variety make anything but general comparisons difficult in this con- 

 nection. 



The studies of kernel development previously reported in the cereals 

 have been the outcome of a wide range of experiments and are too numer- 

 ous to be reviewed in detail. Kudelka (4),^ Lermer and Holzner (5), and 

 many others have published on the origin and development of tissues in 

 the caryopsis as a whole, or even in the entire plant. Some investigations 

 have been specifically devoted to tissues of the pericarp. Johannsen (5), 

 Brenchley (/), Schjerning (6, 7), and numerous others have investigated 

 the chemical changes of growth and maturation. The work of these in- 

 vestigators is referred to later. Their experiments were carried on under 

 relatively unfavorable conditions. The contrast is remarkable between 

 the humid climates of Denmark and England, with their frequent storms 

 and days of low activity, and the arid climate of Aberdeen. Schjerning 

 had a difference of 1 2 days in the maturity of his plots in two succeeding 

 years. 



The detail of the experiment at Aberdeen is more nearly like those of 

 Brenchley (/), Schjerning (6, 7), and Johannsen (5) than those of the 

 other investigators. It differs from these in a reduction of the period 

 between samples and in the extensive study of the physical indices of 

 length and diameter of kernel. The chemical and morphological phases 

 are not comparable with those of Schjerning and Johannsen. 



2 Reference is made by number (italic) to "I,iterature cited," p. 429. 



